I have the right to refuse service to anyone but I wouldn't do it without reason I'll always let you know beforehand why, but here are a couple possible reasons to why.

Being extremely rude and hard to work with

Not following the rules I applied to what's is and not ok to draw

I could be already busy at the moment and you might of asked just a tad bit too late. I apologists if this would be the case but don't worry as this would temporary and you're free to ask me as soon as I'm available again.